His comments come as Boris Johnson — alongside G7 allies — prepares to lobby the US president Joe Biden to grant an additional few days to evacuate desperate citizens and Afghans granted visas from the clutches of the Taliban insurgency.
However, Mr Wallace played down the prospect of an extension on Tuesday, pointing to statements from both the US administration and the warning from a Taliban spokesperson of the “consequences” if foreign powers attempted to retain a military presence in the region beyond the “red line” deadline of 31 August.
“I think it is unlikely,” the defence secretary told Sky News ahead of the G7 meeting.
“Not only because of what the Taliban has said but if you look at the public statements of president Biden, I think it is unlikely. But it’s definitely worth us trying, and we will.”
In a separate interview on ITV, the cabinet minister suggested there was a “slim chance” of the deadline being extended, adding: “That’s why we’ve been planning for the worst, of course we hope for the best”.
The defence secretary also issued a frank warning that the security risk around the airport could increase and “gets more and more dangerous” as the deadline approaches, with terrorist groups potentially attempting to exploit the fragile situation.
He said: “Terrorist groups such as Isis would like to be seen to take greater credit, or like to be seen to chase the West out of the airport — that is inevitably going to feed their narrative and ambitions.
“The Taliban are actually controlling the outer ring of the airport and indeed checkpoints throughout Kabul and that makes it harder for Isis terrorists. The Taliban and Isis have no friendly relationship at all, but we are very mindful that we are very, very vulnerable should these terrorists choose to do something.”
Mr Wallace, who reiterated that “not everyone” will be able to get out of the country, added that in the last 24-hour period, revealed that over 2,000 people had been evacuated from Hamid Karzai International Airport, with the total now exceeding 8,000.
In social media posts ahead of the G7 leaders’ meeting, the prime minister said he will ask “our friends and allies to stand by the Afghan people and step up support for refugees and humanitarian aid”.
“We will continue to use every humanitarian and diplomatic lever to safeguard human rights and the gains made in Afghanistan over the last two decades,” he said. “The Taliban will be judged by their deeds and not their words”.
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